ASoC: Intel: Skylake: Don't unload module when in use

A module may have multiple instances in DSP, so unload only when usage
count is zero.

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>